Varifunction potentiometer



8, 1953 J. J. WILENTCHIK 2,662,144

VARIFUNCTION POTENTIOMETER Filed Sept. 19, 1949 I JERZKI. WIZFNTCHIK l m 4-1- 157 ig fig 7 ATTORNEY.

Patented Dec. 8, 1953 UNITED STATES PATENT OFFICE VARIFUNCTION POTENTIOMETER J erzy J Wilentchik, New York, N. Y.

Application September 19, 1949, Serial No. 116,508

7 Claims.

This invention is in part a continuation of my copending application Serial No. 112,007 filed on August 24, 1949 and relates to improvements in voltage control systems comprising control means, wherein the output voltage 12 can be varied as a function of the displacement c of said control means according to any desirable relationship v=f(ac).

An object of the invention is to provide a system of one afore-mentioned character in which the output voltage function o=f(.r) of the instrument is composed of a desirable number of straight segments, the location, and the slope of each one of the latter being determined individually and set into the instrument in such manner that the exact profile of the desired voltage curve is obtained.

Another object of this invention is to provide means for changing the shape of the output function v"=f(x)' easily and quickly, by unskilled operator, without dismantling the instrument and without stopping its operation.

A still further object of the invention is to provide means for accurate generation of potentials.

The invention applies to control systems, wherein the input from the control means can be expressed by a relatively large number of revolutions of the input shaft. There are known in the art non-linear resistors wound on shaped card-boards, but such an arrangement does not provide means for changing the form of the generated function.

For a better understanding of the invention, its advantages over existing art and the specific objectives attained with its use, reference sho ld be had to the accompanying drawings and to the following specifications in which preferred embodiments of the invention have been illustrated and described.

In the drawings:

Fig. l is a schematic representation of the vari-function potentiometer system according to the invention.

Fig. 2 is a circuit diagram of a modified form of voltage divider according to Fig. 1.

Fig. 3 is a partial cross-section of a voltage divider according to Fig. 2.

Fig. 4 is a transverse section according to Fig. 3.

Fig. 5 is a detail view of the wiping contacts arrangement according to Figs. 2, 3 and 4.

Fig. 6 is a schematic representation of a Vernier, linear potentiometer according to the invention.

Fig. 7 is a view of the intermittent motion coupling according to Fig. 6.

Referring to Fig. 1, there is shown a commutator or a tab array ring I of a regular circular form, the potential of each tab being controlled individually by means of a voltage divider 2 provided with a plurality of adjustable taps, its theory of operation being explained fully with reference to Figs. 3 and 4 in my amended, co-

pending application Serial No. 112,007. The adjustment of respective taps along the length of the resistance 20 can be performed with the assistance of a voltage or resistance measuring instrument, or according to readings of a graduated scale 28 which may be imprinted along the length of pipe containing the resistance 20.

The resistance element 20 is connected across voltage supply terminals 2! and 22 and provided with adjustable taps 23a, 23b, 230, etc. spaced along the circumference of the former and connected by intermediary of conductors 24a, 24b, 240, etc. to respective tabs 2a, 2b, and 2c of the tab-array-ring I. A contact device 3 operatively linked to shaft 1 and composed of two contact elements 4 and 5 insulated from each other and from the shaft 1 is adapted to be moved along the length of the tab-array-ring l, the contact elements t and 5 being in physical engagement with respective tabs 2.

To eliminate the possibility of either contact element 4 or 5 being in physical engagement with two such tabs at the same time, the width of the contact elements 4 and 5 is made less than the width of a tab and less than the width of insulation between a pair of successive tabs. The distance between the elements 4 and 5 is fixed and may be preferably equal or less than the distance between the centers of two successive tabs, all tabs being of course similar to each other. The step motion may be produced through intermediary of a toothed wheel 6 sitting rigidly on shaft 1, the latter concentric to the tab-arrayring and an arm 33 coupled to shaft 9'. A similar arrangement was explained and illustrated previously in my copending application Serial No. 112,607 and a view of it is shown in Fig. 6. Upon every complete revolution of shaft e, the arm 8 will become engaged with the toothed wheel 6 and move it a length corresponding to the tooth width of the latter. The toothed wheel 6 is designed in such a manner that upon each engagement of wheel 6 and arm 8, the contact device 3 would be moved by a distance corresponding to the distance between a pair of successive tabs, or in different words that each one of the contact elements 4 and 5 will be transferred from a respective tab to the next following one. To eliminate the possibility of a loose motion of slider 3, the shaft 1 may be provided with a detent mechanism consisting of a pointer 25 operatively linked to said shaft and adapted to engage yieldingly a notched circumference of an associated stationary disc 26, wherein the radial position of each notch corresponds to the position of a respective tab. The pointer 25 exerts a braking action upon the motion of shaft I whenever a notch is encountered.

The contact devices and {i are connected through intermediary of conductors It and II to respective terminals 52 and it of a resistance element is wound on a ring shaped core in such a manner as to form a ring of a regular circular form. A contact device I5, called generally the output contact device, is associated physica1- 1y with the resistance 54, the former operatively linked to and insulated from shaft 9 and adapted to be moved by the control means I6. The control means can he a hand wheel, a servo, etc.

The operation of this system is as follows:

The potential difference bet men the pair of tabs in and 2b distributed uniformly along the length the re istance it. The pair of tabs and 2b is shown associated with respective eontact elen' ents a The contact device I5 while usted the resistance i l by the con trol means "nly changing on with respect to the term i Assuming that the potential. the tab higher than that 01" the tab to, and that the input f om the control me ns ter s to move the contact device I5 in a direction indicated by an arrow (from the terminal 532 along the resistance element 54 towards the terminal 13), the potential of the moved contact device will decrease uniformly between the limits fined by respective potentials of the terminals l2 and As the contact device i5 is being transferred ir the terminal I3, towards it, thus ternii F one complete revolution of shaft 9, the wheel 6 become engaged, wl disp1ace-- ment of slider 3 by a wid h r tab in the direc tion indicated by an contact elements 4 and ii are associated in w with respective tabs 2b and 20. It is understood of course that the distance between. the terminal i2 and !3 can be equal to or less t an the width of the contact device i5, thus reserving the continuity of the output voltage function. As the shaft ii ed in the same direction, the cpei .ed above would be repeated. if the i... ut irr n the primary control means tended to re e the shaft "l in a reverse direction from above, same explanation would still hold true, except that the arrows should be reversed.

The resistance 5 d sh -i be of course of a sufliciently resistance to allow only a negligible current flow between any two tabs and eliminate thus the eects of potential drop which may cause a considerable inaccuracy of indication.

The potential of the output contact device I5 may be applied to a suitable, high impedance amplifier and operate a motor unit and a follow up means (not shown). As a follow up means an arrangement described in Fig. 6 or any conventional, linearly wound potentiometer could be us rring to Figs. 3, i and 5, there shown a modined form of a voltage divider which can be employed with the org .nization in Fig. 1. The divider resistance element 42 ti consists a wound unilormly on a hollow cylindrical core 34, the latter inside a concentric pipe provided with plurality of longitudinal slots 3t spaced uniformly along its circumference, a plurality of selectors or contact devi es 3'1, contact device composed of a pair of spring leaf contact laments and to to be moved in physical engagement with saidresistance, each to a unit of the voltage divider scale.

slot of pipe 35 serving to guide the motion of its respective contact device 3? while the surface of the pipe between slots serves to press the contact elements 38 and 39 against the resistance element 42 and improve thus the electrical contact. The pipe 35 and the core 34 are made of course of insulating material. The terminals 32 and 33 of the resistance element 42 are connected to the positive and the negative supply wires I46 and I4! respectively of a source of voltage.

The position that each selector should assume to be associated with a correct amount of resistance can be found by a resistance or voltage measuring instrument or by marking a graduated scale (not shown) along the length of each one of the respective slots 36 relative to the values of potential assumed by the contact device in that position. The handle 43 of a selector can be of course insulated from the contact elements proper, thus allowing adjustment while the unit is operating. The contact elements 38 and 39 are spaced at a such distance from each other that the voltage between them is always equal Assuming for example that the length of the divider resistance is ten inches and that there are one hundred scale divisions associated with the motion of the contact device 3?, the distance between the two elements would be approximately 0.1 in. Assuming that the total voltage drop across the resistance 42 is one hundred voltage units, the voltage drop per division would be one unit. Similarly the voltage difference between the contact elements 33 and 39 would be one unit irrespective of position of the contact device ill. If for example, the contact device 3! has been placed opposite the scale division serial No. 47 of the divider 3I, the contact elements 33 and 39 will assume respective potentials of forty-seven and forty-eight voltage units.

Each selector 3'! is provided with a variable resistance 45 (indicated in 2 by the numerals 45a, 45b, 45c, etc.) connected across the wipers 33 and 39 via respective conductors ll and 4B, and provided with a contact wiper 43 (indicated in Fig. 2 b the numerals 46a, 46b, 460, etc. The resistances 45 serve for Vernier adjustment of potential via conductors 24a, 24b 240, etc. applied to respective tabs 2 of the commutator ring seen in Fig. 1, and can be provided with respective graduated scales to facilitate the presetting operation.

According to Figs. 1, 3 and 4, the number of slots 36 in the pipe 35 is not equal to the nurs ber of tabs 2 in the tab array ring I. In actual equipment the number of slots and tabs will be of course the same.

The effect of current taken off by the resist-- ances 45 can. be generally compensated by proper spacing of the contacts 38 and 39 in the selector 3?.

Referring to Fig. GQthere is shown a linear potentiometer operating on a principle similar to the principle of operation of the yari-function potentiometer.

It consists principally of interconnected, circular potentiometer windings I54 and. I63, and of a coupling mechanism comprising a gear E55 linked operatively to shaft I51, of a displacing arm I58 coupled to shaft I56, and of a detent arm I60 cooperating with detent disc I61. The terminals I64 and I65 of the winding I63 connected to respective voltage supply lines 143 and I41. The winding I56 is provided with a pair of wiping contacts i5!) and I5! linked mechanically through an insulated arm I68 to the shaft 551. The terminals i522 and 153 are connected to respective wiping contacts 159 and I5I. A suitable collector ring arrangement (not shown) can be used for this purpose. Upon each complete revolution of the shaft I55 and more particularly simultaneously with a wiper contact I55 crossing the gap between the terminals I52 and W3, the arm 56 engages the gear 59 and displaces the contacts I 59 and I5! by an uniform step motion. The view of the arm I58 and of the gear I59 is shown more clearly in Fig. 7. The distance between the wipers i583 and I5I is set in such a manner, that upon an assumed clockwise step displacement of the arm 66, the wiper I59 will settle relative to the winding I66 at a position occupied subsequently to the displacement by the wiper 155, and vice versa, assuming a counterclockwise displacement of the arm I68, the wiper i5I will settle at a position occupied previously by the wiper I59. Provided, that the resistance ratio of the potentiometer I54 to that of the potentiometer I56 is sufiiciently high, a linearly changing voltage will be obtained at the output wiper I55. Generally, the shaft I 56 is connected to a suitable control mechanism shown at 16c and the Wiper I55 to an electric load circuit. The arrangement in Fig. 6 may be of course modified to serve as a Vernier voltage divider with the shafts I55 and I5! being adjustable manually, independently of each other. In such a modified organization, there is no need for use of the dispacing arm I58, neither of the gear I59.

It should be borne in mind that the invention is applicable not merely to resistance elements but to all types of voltage sources comprising voltage dividing means having adjustable taps from which voltages of diiTerent magnitude, phase, frequency etc. may be obtained.

What I claim as novel, and desire to secure by Letters Patent is:

l. A functionally adjustable voltage division device comprising in combination, a pair of terminals, voltage division means connected between said pair of terminals, a plurality of contact elements disposed on said voltage division means, means to adjust said contact elements along the length of said division means between said terminals, an impedance component adapted to be connected to said elements, a third terminal, and a wiping contact device con nected to said third terminal and adapted for displacement along the length of said impedance component.

2. A functionally adjustable voltage divider comprising in combination, voltage division means, a plurality of contact elements disposed on said voltage division means, means to adjust said contact elements along the full length of said division means, an impedance component, wiping contact device adapted for displacement along the length of said component, and means for connecting and disconnecting any two consecutive ones of said elements and said component in predetermined relation to the movement of said wiping contact device.

3. A functional voltage division device, comprising in combination, a single 360 arc impedance element, wiping means, control means for traversing said wiping means along the length of said element, voltage division means comprising a plurality of series connected impedance sectors, intermittently actuated switching means for disconnecting one while connecting next consecutive one of said impedance sectors in shunt with said impedance element, and means to actuate said switching means in predetermined relation to the movement of said wiping means.

4. A functionally adjustable voltage divider comprising in combination, voltage division means, plurality of contact elements disposed on said voltage division means, means to adjust said contact elements along the full length of said division means in accordance with a predetermined law, a plurality of studs connected to respective ones of said elements, single impedanoe component, wiping contact device adapted for displacement along the length of said component, switching means for connecting and disconnecting said component and any two con secutive ones of said studs, and means to actuate said switching means in predetermined relation to the movement of said contact device.

5. In combination, a single 360 arc impedance element, wiping means, control means for traversing said wiping means along the length of said element, a plurality of studs, means to apply variable potential to respective ones of said studs, intermittently actuated switching means for connecting and disconnecting said impedance element and any two consecutive ones of said studs, and means to actuate said switching means in a predetermined relation to the movement of said wiping means.

6. In combination, a voltage division means, a plurality of contact elements disposed on said division means, means to adjust respective ones of said contact elements along the length of said division means, a plurality of studs connected to respective ones of said elements, wiping means cooperating conductively with said studs, and means to adjust said wiping means along the length of said studs.

7. In combination, voltage division means, rail means disposed around and along the length of said division means, a plurality of contact elements, interlock means between said rail means and said elements to maintain the latter to conductive engagement with said division means, said interlock means comprising a cavity in said rail means and dimensionally corresponding proturberances in said elements, said protuberances being interlocked within said cavity, and means to adjust said interlocked elements along the length of said division means.

JERZY J WILEN'I'CI-IIK.

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